Method for keeping metal mold in a clamped state

ABSTRACT

A method and device for keeping metal mold in a clamped state characterized in that the mold-halves of the metal mold are respectively coupled to a plurality of hydraulic cylinders and pistons, the mold-halves are forced to close so that the displacement of the pistons causes a hydraulic fluid to flow from one space to the other in the hydraulic cylinders and also to an accumulator through a control valve, and upon the completion of the closure, shifting the control valve to another position so that the remaining fluid in the above mentioned one space is further evacuated to another accumulator at a low pressure with the simultaneous communication maintained between the other space of the hydraulic cylinders and the first accumulator, whereby a pressure difference is created between the two spaces separated by the pistons, and the mold-halves are thereby clamped.

United States Patent Aoki 51 3,700,765 it?! Q ,1972

[54] METHOD FOR KEEPING METAL MOLD IN A CLAMPED STATE [72] Inventor: Katashi Aoki, 6037 Oaza Minamijo,

Hanishina-gun, Japan [22] Filed: May 20, 1971 [21] Appl. No.: 145,385

[30] Foreign Application Priority Data May 30, 1970 Japan ..45/46688 [52] US. Cl. ..264/328, 269/30, 425/450 [51] Int. Cl ..B29f l/06, B30b 15/16 [58] Field of Search ...425/450, 451; 18/301; 269/30, 269/34 [56] References Cited UNITED STATES PATENTS 2,862,238 10/1958 Cuzzi ..425/450 2,681,471 6/1954 Heinzelman ..425/450 3,191,235 I 6/ 1965 Rougement ..425/450 3,567,098 3/1971 Maynard ..227/130 Primary Examiner-Robert F. White Assistant Examiner-T. E. Balhoff Attomey-David H. Semmes [57] ABSTRACT A method and device for keeping metal mold in a clamped state characterized in that the mold-halves of the metal mold are respectively coupled to a plurality of hydraulic cylinders and pistons, the mold-halves are forced to close so that the displacement of the pistons causes a hydraulic fluid to flow from one space to the other in the hydraulic cylinders and also to an accumulator through a control valve, and upon the completion of the closure, shifting the control valve to another position so that the remaining fluid in the above mentioned one space is further evacuated to another accumulator at a lowpressure with the simul- ?taneous communication maintained between the other .space of the hydraulic cylinders and the first accumulator, whereby a pressure difference is created between the two spaces separated by the pistons, and the mold-halves are thereby clamped.

1 Claim, 4 Drawing Figures PATENTEDflB-T 24 I97? 3 700. 765

SHEET 1 or 2 INVENTOR.

/(n msh/ 190m WWW/M PATENIED 24 I97? 3 700 7655 saw 2 BF 2 I INVENTOR. Kp-M HI /7oki METHOD FOR KEEPING METAL MOLD IN A CLAMPED STATE This invention relates to a method and device for clamping metal mold used in the formation ofsynthetic resin and in the die-casting.

The metal mold provided in the conventional synthetic resin forming machine or the like has been so constructed that the both halves of the metal mold are respectively attached to a stationary plate and a movable plate of the mold clamping mechanism, the mold halves being closed by the outer force exerted to the movable plate, and are then clamped in the closed state.

Furthermore, a set of metal molds-provided in the conventional rotary type forming machine have been mounted on a pair of upper and lower rotating plates provided in the mold clamping device, and are so constructed that the mold closure and clamping are attained by the outer force applied to the movable metal mold side although the metal mold can be shifted in its closed state.

In either of the above described cases, the metal mold or molds are always combined with the mold clamping device, and the metal molds cannot be clamped without the mold clamping device nor be kept in the clamped state without a pressing device acting on the metal molds from outside.

Therefore, a primary object of the present invention is to be provided a method and device for maintaining the metal molds in a clamped condition without the pressing device acting on the metal molds from outside.

Another object of the present invention is to provide a method and device for maintaining the metal mold in a clamped and pressurized condition while the metal mold filled with a synthetic resin or a die-casting material is shifted to a mold opening-or-closing device.

Still another object of the present invention is to provide a method and device for keeping the metal mold in a clamped and pressurized condition in such a manner that the opening of the metal mold is not possible unless a hydraulic pressure acting on the pistons in a plurality of hydraulic cylinders coupled to the metal mold is removed.

These and other objects of the present invention are achieved by a method for keeping the metal mold in a clamped and pressurized condition, which comprises the steps of preparing a plurality of hydraulic cylinders and pistons included therein to be coupled to the moldhalves respectively, forcing to close the mold for displacing the pistons in the hydraulic cylinders and shifting the hydraulic fluid from a space to another space in the cylinder and also to an accumulator, and shifting a control valve to another position for evacuating the hydraulic fluid remaining in one of the spaces to another accumulator at a low pressure and for causing a pressure difference acting on the pistons.

In another aspect of the invention, the objects can be achieved by a device for practicing the above described method, comprising a plurality of hydraulic cylinders including pistons, a pair of base plates coupled to the hydraulic cylinders and the pistons respectively, a pair of mold-halves mounted on the confronting surfaces of the base plates, hydraulic oil paths for passing the hydraulic oil in one of the spaces in each of the hydraulic cylinders to the other under the action of the piston moved by an outer force and also to an accumulator,

and a valve means for interrupting an oil path between the two spaces and evacuating remaining hydraulic fluid in said one of the spaces to another accumulator for creating a pressure difference exerted to the pistons. The nature, principle, and utility of the present invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a front view, partially in section, of a device for keeping the metal mold in a clamped state, which constitutes an embodiment of the present invention;

FIG..2 is'a view similar to FIG. 1 of the same device wherein the metal mold is closed;

FIG. 3 is a partial view of the same device wherein the metal mold is going to be closed; and

FIG. 4 is a partial view of the same device wherein the metal mold is going to be opened.

In the drawings, a male mold-half 1 and a female mold-half 2 are respectively mounted on base plates 3 and 4. At four comers of the base plates 3 and 4, there are provided hydraulic cylinders 5, 5, each including a piston 6 having a rod portion 7. The rod portions 7, 7,

are fixed to the base plate 3, and the hydraulic cy1in-.

ders 5, 5, are fixed to the base plate 4 at tube portions 8, 8, of the hydraulic cylinders, so that the two moldhalves 1 and 2 may be thereby open-or-closed freely. The upper part and the lower part of the hydraulic cylinders 5, 5, are connected to hydraulic oil paths 9 for flowing the operative oil caused by the displacement of the pistons 6, 6, inside of the hydraulic cylinders 5, 5. The hydraulic oil paths 9 are composed of a bladder type accumulator 10 for storing one part of the operative fluid pushed out of the cylinders 5, 5, by means of the pistons 6, 6, and for supplying the operative fluid to the cylinders 5, 5, when it is desired, another bladder type accumulator 11 and a check valve 15 for evacuating a part of the operative fluid from the lower space in each of the hydraulic cylinders 5, 5, and thereby reducing the pressure in the lower space of the cylinder 5, 5, and a valve means 12 which may be transferred between a first position and a second position for controlling the flow of the operative fluid. In the drawings, numerals 13 and 14 designate open-or-closing members for the metal mold.

The operation of the device will now be explained.

When it is desired that a pair of mold-halves opened by pulling the base plate 3 upwardly by means of the mold opening-or-closing device as shown in FIG. 1 are closed as shown in FIG. 2 into a pressurized condition, the valve means 12 of the hydraulic oil paths 9 is shifted to its pass-through position as shown in FIG. 3 and forces the male mold-half 1 on the base plate 3 down to the other mold-half 2 on the base plate 4. Depending on the movement of the base plate 3, the pistons 6, 6, are moved inside of the tubes 8, 8, of the hydraulic cylinders 5, 5, downwardly, and the operative fluid in the lower space of the hydraulic cylinders 5, 5, is pushed out of the cylinders to the upper space of the same hydraulic cylinders and also to the accumulator 10 through the valve means 12 placed at its passthrough position. In this case, the amount of the fluid passed into the accumulator 10 corresponds to the difference of the volumes of the fluid pushed out of the lower space of the hydraulic cylinder and of the fluid introduced into the upper space of the same cylinder because of the existence of the piston rod 7. As a result the pressure in the accumulator 10 is elevated.

When the base plate 3 is fully descended so that the male mold-half l engages the female mold-half 2 on the base plate 4, there is no recognizable pressure difference between the upper space and the lower space of the hydraulic cylinder 5 separated by the piston 6, and since the valve means 12 is in the pass-through position (hereinafter called the first position), the mold-halves may be easily opened if an outer force is exerted on the base plate 3 upwardly as indicated by an arrow mark in FIG. 4.

In order to keep the mold-halves in a clamped and pressurized condition, the valve means 12 is transferred to a one port blocking position (hereinafter called the second position), asshown in FIG. 2. As a result, the hydraulic fluid remaining in the lower space of the hydraulic cylinders 5, 5, is communicated to the accumulator 11, whereby the pressure in the lower space is decreased to a lower value. However, the upper space of the hydraulic cylinders 5, 5, is still communicated with the accumulator at a high pressure, and for this reason, a pressure difference is created between the upper space and the lower space of the hydraulic cylinders 5, 5, which urges the pistons 6, 6, downwardly. By this way, the metal mold-halves l and 2 are firmly clamped, and any application of outer force cannot open the mold-halves.

When it is desired to open the metal mold, the valve means 12 is shifted back to its original position as shown in FlG. 4. Thus the pressure difference between the upper and lower spaces of the hydraulic cylinders 5, 5, is eliminated, and the metal mold-halves can be easily opened by raising the base plate 3 upwardly, for instance, by means of the mold opening-or-closing device. In that case, the hydraulic fluid in the upper space of the hydraulic cylinders 5, 5, can be shifted back to the lower space thereof through the valve means 12 at the pass-through position. During the above described procedure, the hydraulic fluid stored in the accumulators 10 and 11 is passed into the lower space of the hydraulic cylinders 5, 5, under the suction caused by the rising pistons 6, 6, whereby the whole system is brought back to its initial condition as shown in FIG. 1.

According to the present invention, since the metal mold thus closed is further clamped employing a plurality of hydraulic cylinders coupled to the mold-halves in a freely openable and closable manner, the metal mold can be maintained in the clamped state even after the metal mold is removed from the injection molding machine, and the metal mold can withstand the inner pressure caused by the synthetic resin filled inside of the metal mold because of the oil pressure inside of the hydraulic cylinders which can be removed only by shifting the control valve means to another position.

Furthermore, the device is constructed simply by coupling the hydraulic cylinders to the mold-halves so that the mold-halves can be freely open-or-closed through the operation of the hydraulic cylinders, and the transportation of the device is also very easy. For this reason, it is apparent that the method and the device according to the present invention can afford various advanta eo featu e such as e ablin the transportation m oldiii g which has been d1 icult l l'l the conventional apparatus.

What is claimed is:

l. A method for keeping metal mold in a clamped state during filling comprising the steps of preparing a plurality of hydraulic cylinders and pistons respectively coupled to the mold-halves, forcing to close said moldhalves so that the displacement of the pistons causes the hydraulic fluid to flow from one space to the other in said hydraulic cylinders and also to an accumulator through a control valve means, and shifting said control valve means to another position at the completion of the closure of the mold-halves so that the remaining fluid in said one space is further evacuated to another accumulator at a low pressure with the simultaneous communication maintained between the other space of the hydraulic cylinders and the first accumulator, whereby a pressure difference is created between the spaces separated by the pistons in said hydraulic cylinders, and the mold-halves are thereby clamped, and then filling the mold. 

1. A method for keeping metal mold in a clamped state during filling comprising the steps of preparing a plurality of hydraulic cylinders and pistons respectively coupled to the moldhalves, forcing to close said mold-halves so that the displacement of the pistons causes the hydraulic fluid to flow from one space to the other in said hydraulic cylinders and also to an accumulator through a control valve meanS, and shifting said control valve means to another position at the completion of the closure of the mold-halves so that the remaining fluid in said one space is further evacuated to another accumulator at a low pressure with the simultaneous communication maintained between the other space of the hydraulic cylinders and the first accumulator, whereby a pressure difference is created between the spaces separated by the pistons in said hydraulic cylinders, and the mold-halves are thereby clamped, and then filling the mold. 